The present invention relates to a function circuit incorporating type wiring device for an automobile, and more particularly to a function circuit incorporating type wiring device for an automobile, including a junction block as a main element and an electronic unit pack as a subelement detachably connected to the junction block, so as to increase current capacity of a through circuit formed on a printed board and make the electronic unit pack compact.
Conventionally, an electric wiring for an automobile employs a junction block connectively incorporating a plurality of wiring boards and terminals (connectors) thereof, which wiring boards are provided with many relays, fuses and bus bar circuits on an insulating substrate, for the purpose of simplifying production of a wire harness and mode of the wiring. For example, it has been proposed that a plurality of junction blocks are arranged at suitable positions in a compartment to control various loads (electrical parts) by a main wiring having less branched lines and a branched wiring (Japanese Patent Publication No. 57-34132).
However, the electrical parts to be installed in the automobile have been recently increased because safety of the automobile is pursued and requirement of improvement in comfortability. As a result, the wire harness is made large and complicated, and the junction block itself is also made complicated in structure because of addition of the relay and fuse, etc. To decrease the number of electrical wires in the wire harness and simplify the internal structure of the junction block, there has been develped a system wherein a function circuit is incorporated in the junction block so as to process a part of operation by an input signal to the junction block and generate an output after processed. As a typical example of the system, there has been proposed a function circuit incorporating type wiring device including a connector for directly transmitting input and output signals to a function circuit section not through the junction block, for the purpose of decreasing the number of the bus bar in the junction block.
However, even in the case of using of the junction block that incorporates the function circuit therein, if any electrical parts are added, or a specification is partially changed, it is necessary to change the internal or external structure of the junction block. Accordingly, there has been recently proposed another system wherein an electronic unit pack acting as a sub-junction block is detachably connected to a main junction block (optionally, plural junction blocks), so that the pack may be exchanged to quickly meet the requirements.
Such an electronic unit pack connected to the junction block as mentioned above naturally includes a through circuit that is used in the pack and is led to the outside from a viewpoint of connective function.
FIGS. 6a and 6b show an exemplary electronic unit pack to be connected to the junction block in the prior art. Referring to FIGS. 6a and 6b, reference numerals 1, 2 and 3 designates a junction block, an electronic unit pack and a connector connected to an end of a wire harness W, respectively. A junction block connector 5 and an external connector 6 are provided on an outer periphery of a case 4 of the pack 2.
As shown in FIG. 6b, a circuit led from the junction block 1 through the connector 5 to the pack 2 is comprised of a signal circuit 8 led into an electronic unit 7 only, an output circuit 9 led out from the unit 7, and through circuits 10a and 10b. The through circuits are comprised of a circuit 10a led into the electronic unit 7 and branched out therefrom and a circuit 10b passing through the pack 2 as it stands. The through circuits 10a and 10b and the output circuit 9 are electrically connected with connector terminals (not shown) in the external connector 6. The electronic unit 7 forms a function circuit by requisite electronic devices such-as resistor, capacitor, transistor, IC, LSI and relay, electronic parts and a printed board which will be hereinafter described.
FIGS. 7a and 7b show an internal structure of the pack 2 in FIG. 6a. In an example shown in FIG. 7a, the junction block connector 5 and the external connector 6 are fixed to separate printed boards 11a and 11b in the case 4, respectively. Both the connectors 5 and 6 are arranged reversely to each other, and the printed boards 11a and 11b are electrically connected with each other by jumping wires 12 or the like. In another example shown in FIG. 7b, the connector 5 is directly fixed to a printed board 11c, and the connector 6 is fixed to the case 4 or the printed board 11c. A connection terminal 13 of the connector 6 is formed in a U-shape to absorb a level difference h between the connector 6 and the printed board 11c.
Referring back to FIG. 6a, a case 14 of the junction block 1 incorporates a bus bar wiring board (not shown) having a desired circuit arrangement and a function circuit. Further, the junction block 1 includes a pack connector 15, external connectors 16, fuse 17, fuse holder 18 and relay 19.
In the conventional function circuit incorporating type wiring device constituted of the junction block 1 and the pack 2, as the through circuits 10a and 10b are necessarily formed on the printed boards 11a to 11c, permissible current cannot be made large. Further, as the junction block connector 5 and the external connector 6 are directly fixed onto the printed board, a fixed mounting space is required to cause a decrease in a mounting space for the electronic unit, rendering the pack 2 relatively large-scale as a whole.